Method and System for Measuring Length, Using Mobile Terminal

ABSTRACT

A user measures a length of a target using a mobile terminal and measure a length, irrespective of time and place. The mobile terminal and the target are photographed together in front of the mirror, and a size of the target is estimated using a ratio of the pictured size versus the actual size of the mobile terminal. The actual size of the target is calculated by adjusting the estimated length with an error associated with a difference between a distance from the mirror to the mobile terminal and a distance from the mirror to the target, and thus, a length is more accurately measured. In addition, the error associated with the distance is corrected based on the photographed picture and data stored in a database and thus, a separate distance measurement sensor for correcting the distance is not required and the cost may be reduced.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit under 35 U.S.C.§119(a) of Korean Patent Application No. 10-2013-0133423, filed on Nov.5, 2013, which is hereby incorporated by reference for all purposes asif fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and system for measuring alength using a mobile terminal, and more particularly, to a method andsystem for measuring a length using a mobile terminal that measures alength of a target of measurement.

2. Description of the Prior Art

Rapidly increased use of a mobile terminal enables continuousdevelopment of various functions that may be utilized for the real lifeusing the mobility of the mobile terminal. Among those functions,various length measuring methods using the mobile terminal have beenprovided.

According to Korean Patent No. 10-0652685, the disclosure provides amethod of calculating the actual length of a target of measurement basedon the distance to the target of measurement, obtained using a distancemeasurement sensor, and an image of the target of measurementphotographed using a camera.

However, a general mobile terminal does not include a sensor formeasuring a distance, such as, a ultrasonic sensor, a infrared sensor,and the like, and thus, the user of the general mobile terminal cannotutilize the described function. In addition, the sensor, such as theultrasonic sensor, the infrared sensor, and the like is expensive andthus, when the expensive sensor is installed in the mobile terminal, theprice of the mobile terminal may be increased.

SUMMARY OF THE INVENTION

An aspect of the present invention is to provide a method and system formeasuring a length using a mobile terminal that may readily measure thelength of a target of measurement.

In accordance with an aspect of the present invention, a method ofmeasuring a length using a mobile terminal is provided. The methodincludes: photographing, by a user, a picture of the mobile terminal anda target of measurement together in front of a mirror, using a camera ofthe mobile terminal; obtaining a ratio of a size of the mobile terminalin the picture to an actual size of the mobile terminal, and estimatinga length of the target of measurement from a size of the target ofmeasurement in the picture, using the ratio; and calculating an actuallength of the target of measurement based on the estimated length and adifference between a distance from the mirror to the mobile terminal anda distance from the mirror to the target of measurement.

In accordance with another aspect of the present invention, a lengthmeasurement system is provided. The system includes: a camera that isincluded in a mobile terminal and photographs a target of measurement infront of a mirror; a database that stores an actual size of the mobileterminal and error data associated with a difference between a distancefrom the mirror to the mobile terminal and a distance from the mirror tothe target of measurement; and a calculator that obtains a ratio of asize of the mobile terminal in the picture to the actual size of themobile terminal, based on the picture photographed by the camera,estimates a length of the target of measurement from the size of thetarget of measurement in the picture using the ratio, and adjusts theestimated length with the error data, so as to calculate an actuallength of the target of measurement.

According to embodiments of the present invention, a user measures alength of a target of measurement using a mobile terminal and thus, mayreadily measure a length, irrespective of time and place.

In addition, according to embodiments of the present invention, a mobileterminal and a target of measurement are photographed together in frontof a mirror, and a size of the target of measurement is estimated usinga ratio of a size of the mobile terminal in a picture to an actual sizeof the mobile terminal, and thus, the measurement is readily executed.

In addition, according to embodiments of the present invention, anactual size of a target of measurement is calculated by adjusting theestimated length with an error associated with a difference between adistance from a mirror to a mobile terminal and a distance from themirror to the target of measurement and thus, a length is moreaccurately measured.

In addition, according to embodiments of the present invention, an errorassociated with a distance is corrected based on a photographed pictureand data stored in a database and thus, a separate distance measurementsensor for correcting the distance is not required and the cost may bereduced.

In addition, according to embodiments of the present invention, ageneral mobile terminal that does not include a distance measurementsensor may measure a length.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more apparent from the following detailed descriptionin conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram schematically illustrating a lengthmeasurement system according to an embodiment of the present invention;

FIG. 2 is a diagram illustrating photographing of a front side pictureof a target of measurement in a length measurement method according toan embodiment of the present invention;

FIG. 3 is a diagram illustrating photographing of a lateral side pictureof a target of measurement in a length measurement method according toan embodiment of the present invention;

FIG. 4 is a flowchart illustrating a length measurement method accordingto an embodiment of the present invention; and

FIG. 5 is a diagram illustrating an example of an error expressed in apercentage, which is associated with a difference in distance, accordingto an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to accompanying drawings.

Referring to FIG. 1, a length measurement method using a mobile terminalaccording to an embodiment of the present invention may include a mobileterminal 10 including a camera 11, an input unit 12, a terminalcontroller 13, a display unit 14, a memory unit 17, a database 15, acalculator 18, and a terminal communication unit 16.

The mobile terminal 10 includes various terminals equipped with thecamera 11, such as a portable phone, a net book, a tablet PersonalComputer (PC), and the like. In addition, the mobile terminal 10includes a camera equipped with a communication function.

The camera 11 is a device that is included in the mobile terminal 10,and is used for photographing a target which is desired to be measuredby a user. Here, the target of measurement may include various dailynecessities, school supplies, furniture, a body part, or the like.

The input unit 12 is included in the mobile terminal 10, and selects orinputs information desired by the user, and has a function for editingan image photographed by the camera 11. The input unit 12 includes abutton including a number or a character, or a touch unit that isincluded in the display unit 14 and to which a touch of a finger or apen is input. The user may input an actual size (length) of the mobileterminal 10 through the input unit 12.

The terminal controller 13 executes a control to store the imagephotographed by the camera 11 in the memory unit 17, controls thecalculator 18 to calculate an actual length of the target of measurementaccording to the method to be described below, and controls the displayunit 14 to display the calculated actual length of the target ofmeasurement.

The display unit 14 displays the image photographed by the camera 11,information input through the input unit 12, and the like. The displayunit 14 may include a screen providing visual expression through acharacter or an image and a speaker providing acoustic expressionthrough sound.

The memory unit 17 stores an image photographed by the camera 11, or anestimated length or an actual length of the target of measurement,calculated according to the method to be described below. The memoryunit 17 includes the database 15.

In the database 17, device type and model information of the mobileterminal 10, error data obtained in advance through experimentation,based on a distance between the mirror and the mobile terminal and adistance between the mirror and the target of measurement, distance dataassociated with a distance between the mirror and the mobile terminal,obtained in advance through experimentation, based on a ratio of a sizeof the mobile terminal 10 in the picture and an actual size of themobile terminal 10, and the like are stored in advance. The device typeand model information of the mobile terminal 10 includes actual sizes ofvarious types of mobile terminals 10 that are commonly used. The actualsize of the mobile terminal 10 includes a horizontal length, a verticallength, a thickness, a shape, and the like. Information stored in thedatabase 15 may be updated through communication between the mobileterminal 10 and a central server 20 that is to be described below.

The terminal communication unit 16 transmits and receives informationto/from a server communication unit 25 of the central server 20. Theterminal communication unit 16 transmits and receives informationto/from the server communication unit 25, through a mobile network. Theterminal communication unit 16 and the server communication unit 25 maydirectly transmit and receive information without using the mobilenetwork.

The calculator 18 obtains a ratio of the size of the mobile terminal inthe picture to the actual size of the mobile terminal 10 based on thepicture photographed by the camera 11, estimates a length of the targetof measurement from the size of the target of measurement in thepicture, using the ratio, and calculates an actual length of the targetof measurement by adjusting the estimated length with the error data.Although the present embodiment exemplifies that the calculator 18 isincluded in the mobile terminal 10, this may not be limited thereto, andthe calculator 18 may be included in the central server 20.

The central server 20 is a type of computer including a servercommunication unit 25 that communicates with the terminal communicationunit 16 through the mobile network. The central server 20 may be acomputer of a telecommunication company that provides the mobilenetwork, or may be a computer of a company that provides a lengthmeasurement Application (App.) which provides a length measurementmethod to be described below.

A length measurement method according to an embodiment of the presentinvention configured as described above will be described as follows.

Referring to FIG. 4, a user photographs a target 30 of measurement usingthe camera 11 of the mobile terminal 10 in operation S1. Although thepresent embodiment exemplifies that the target 30 of measurement is arectangular parallelepiped shape, this may not be limited thereto, andmay be applied to various shapes.

When the target 30 of measurement is photographed, guidance about aphotographing method may be displayed through the display unit 14. Theguidance may be provided through voice or characters. Although thepresent embodiment exemplifies that the guidance is provided throughvoice since the user has difficulty in viewing the mobile terminal 10during photographing, this may not be limited thereto, and may beprovided through both characters and voice. The photographing method mayinclude information associated with a relative position of the mobileterminal 10 and the target 30 of measurement, and information associatedwith a resolution for photographing. The photographing method providesguidance helping the user photograph the mobile terminal 10 and thetarget 30 of measurement, together.

In the photographing operation, the user may photograph at least one ofa front side picture and a lateral side picture of the target 30 ofmeasurement. The present embodiment exemplifies that the front sidepicture and the lateral side picture of the target 30 of measurement arephotographed.

Referring to FIG. 2, when the user photographs the front side picture ofthe target 30 of measurement, the user disposes the target 30 ofmeasurement, in front of the mirror 2, in the forward direction wherethe target 30 of measurement faces the mirror 2, matches the center ofthe front side of the mobile terminal 10 to the center of the front sideof the target 30 of measurement, and photographs the front side pictureof the target 30 of measurement. When the mobile terminal 10 is incontact with the target 30 of measurement or when a distance between themobile terminal 10 and the target 30 of measurement is relatively close,in the front side picture, a difference between a distance (Mirror ToPhone (MTP)) from the mirror 2 to the mobile terminal 10 and a distance(Mirror To Object (MTO)) from the mirror 2 to the target 30 ofmeasurement may be ignored. In this instance, an error (Phone DistanceAdjustment (PDA)) may not need to be corrected and thus, a length may bemeasured only through the front side picture. There may be a case ofhaving difficulty in matching a location between the mobile terminal 10and the target 30 of measurement during photographing the front sidepicture, and thus, a distance between the mobile terminal 10 and thetarget 30 of measurement is significantly distant. In this instance, theerror (PDA) between the distance (MTP) from the mirror 2 to the mobileterminal 10 and the distance (MTO) from the mirror 2 to the target 30 ofmeasurement may need to be corrected and thus, the lateral side pictureis need to be photographed in addition to the front side picture.

Referring to FIG. 3, when the user photographs the lateral side pictureof the target 30 of measurement, the user disposes the target 30 ofmeasurement in a lateral direction from the mirror 2, in front of themirror 2, matches the center of the lateral side of the mobile terminal30 to the center of the front side of the target 30 of measurement, andphotographs the lateral side picture of the target 30 of measurement.Referring to FIGS. 2 and 3, although it has been exemplified that thefront side picture and the lateral side picture of the target 30 ofmeasurement are photographed, this may not be limited thereto, andphotographing is executed in various methods based on a shape or a sizeof the target 30 of measurement. The photographed picture is stored inthe memory unit 17.

When photographing is completed, the calculator 18 obtains a ratio ofthe size of the mobile terminal 10 in the picture to the actual size ofthe mobile terminal 10 from the photographed picture, and estimates alength of the target 30 of measurement from the size of the target 30 ofmeasurement in the picture, using the ratio, in operation S2. Here, theactual size of the mobile terminal 10 may be obtained from the devicetype information of the mobile terminal 10 that is stored in advance inthe database 15. When the actual size of the mobile terminal 10 is notobtained from the device type information, the information may beseparately input by the user. The ratio of the size of the mobileterminal 10 in the picture to the actual size of the mobile terminal 10,is identical to a ratio of a size of the target 30 of measurement in thepicture to a size of the target 30 of the measurement. Therefore, thesize of the target 30 of measurement may be estimated based on theratio. The size of the target 30 of measurement estimated by applyingthe ratio is referred to as an estimated size (Estimated Length (EL)).

When the ratio is applied, an error may occur due to a differencebetween a distance from the mirror 2 to the mobile terminal 10 and adistance from the mirror 2 to the target 30 of measurement. Therefore,an Actual Length (AL, Actual Length) of the target 30 of measurement maybe calculated by correcting the difference between the distance from themirror 2 to the mobile terminal 10 and the distance from the mirror 2 tothe target 30 of measurement, with respect to the estimated size (EL) inoperations S3 through S6.

An operation of calculating the actual length (AL) of the target 30 ofmeasurement by correcting the difference in distance may includeobtaining the distance between the mirror 2 and the mobile terminal 10in operation S3, obtaining the distance between the mirror 2 and thetarget 30 of measurement in operation S4, obtaining an error (PDA, PhoneDistance Adjustment) associated with the difference between the distancefrom the mirror 2 to the mobile terminal 10 and the distance from themirror 2 to the target 30 of measurement in operation S5, and correctingthe obtained error (PDA) with respect to the estimated size (EL) inoperation S6.

The error (PDA) associated with the difference in distance may beobtained from error data that is obtained in advance throughexperimentation, based on the distance (MTP) between the mirror 2 andthe mobile terminal 10, and the distance (MTO) between the mirror 2 andthe target 30 of measurement. The error data is stored in the database15. When the distance from the mirror 2 to the mobile terminal 10 andthe distance from the mirror 2 to the target 30 of measurement aregiven, the error (PDA) associated with the difference in distance may beobtained.

FIG. 5 illustrates an example of an error expressed in a percentage,which shows how small the estimated size (EL) is as compared to theactual size (AL), based on a difference in distance, throughexperimentation.

A result of the experimentation associated with the error may be changedby software of the mobile terminal 10, a camera of the mobile terminal10, a thickness of the mirror 2, and the like.

Referring to FIG. 5, when a distance (MTP) between the mirror 2 and themobile terminal 10 is 30 cm and a distance (MTO) between the mirror 2and the target 30 of measurement is 70 cm and 90 cm, the percentage ofan error indicating a percentage of an estimated size (EL) to an actualsize (AL) is 59% and 49%. Conversely, when the distance (MTP) betweenthe mirror 2 and the mobile terminal 10 is 50 cm, as the distance (MTO)between the mirror 2 and the target 30 of measurement is extended from70 cm to 90 cm, the percentage of the estimated size (EL) to the actualsize (AL) is changed from 81% to 69%. That is, the percentage of theerror is changed based on a difference between the distance (MTP) fromthe mirror 2 to the mobile terminal 10 and the distance (MTO) from themirror 2 to the target 30 of measurement. Therefore, it is important toaccurately know both the distance (MTP) between the mirror 2 and themobile terminal 10 and the distance (MTO) between the mirror 2 and thetarget 30 of measurement.

Referring to FIG. 2, a method of obtaining an actual horizontal length(AL) of the target 30 of measurement will be described.

First, a horizontal length (EL1) of the target 30 of measurement may beestimated using the ratio of the size of the mobile terminal 10 in thepicture to the actual size of the mobile terminal 10. The size of themobile terminal 10 in the picture may be obtained using universalsoftware. The universal software includes all programs that may becapable of obtaining a pixel value of a target from a picture or animage. A pixel value associated with the size of the mobile terminal 10in the picture may be obtained through the universal software and thus,the ratio of the pixel value associated with the size of the mobileterminal in the picture to the actual size of the mobile terminal 10 maybe obtained. A pixel value associated with the horizontal length of thetarget 30 of measurement in the picture is known and thus, thehorizontal length (ED) of the target 30 of measurement may be estimatedusing the ratio. A estimation equation of the horizontal length (ED) ofthe target 30 of measurement is as follows.

(Estimation Equation)

the actual size of the mobile terminal: the pixel value associated withthe size of the mobile terminal in the picture=the actual size of thetarget of measurement: the pixel value associated with the size oftarget of measurement in the picture.

The actual length (AL) may be calculated by adjusting the estimatedhorizontal length (EL1) with the error associated with the differencebetween the distance (MTP) from the mirror 2 to the mobile terminal 10and the distance (MTO) from the mirror 2 to the target 30 ofmeasurement.

To adjust the estimated length with the error associated with thedifference in distance, in FIG. 2, a distance (MTP1) between the mirror2 and the mobile terminal 10 and a distance (MTO1) between the mirrorand the target 30 of measurement are obtained in operations S3 and S4.

The distance (MTP1) between the mirror 2 and the mobile terminal 10 maybe obtained from distance data obtained in advance throughexperimentation, based on the ratio of the size of the mobile terminal10 in the picture to the actual size of the mobile terminal 10. That is,as the distance (MTP1) between the mirror 2 and the mobile terminal 10becomes close, the ratio becomes low, and as the distance (MTP1) betweenthe mirror 2 and the mobile terminal 10 becomes distant, the ratiobecomes high. Accordingly, when the ratio is given, the distance (MTP1)between the mirror 2 and the mobile terminal 10 may be obtained.Therefore, the distance data associated with the distance (MTP1) betweenthe mirror 2 and the mobile terminal 10 is obtained in advance throughthe experimentation and is stored in the database 15 in advance.Therefore, the distance (MTP1) between the mirror 2 and the mobileterminal 10 may be obtained from the distance data.

In FIG. 2, the picture is photographed by disposing the mobile terminal10 significantly close to the target 30 of measurement and thus, thedistance (MTO1) between the mirror 2 and the target 30 of measurement 30is equal to a value obtained by adding the distance (MTP1) between themirror 2 and the mobile terminal 10 and a thickness of the mobileterminal 10. Both the distance (MTP1) between the mirror 2 and themobile terminal 10 and the thickness of the mobile terminal 10 are givenand thus, the distance (MTO1) between the mirror 2 and the target 30 ofmeasurement may be also obtained. However, this may not be limitedthereto. When the picture is photographed by disposing the mobileterminal 10 significantly close to the target 30 of measurement, and itis determined that the thickness of the mobile terminal 10 issignificantly small as compared to the size of the target 30 ofmeasurement, the thickness of the mobile terminal 10 is ignored and itis determined that the distance (MTP1) between the mirror 2 and themobile terminal 10 is equal to the distance (MTO1) between the mirror 2and the target 30 of measurement.

After obtaining the distance (MTP1) between the mirror 2 and the mobileterminal 10 and the distance (MTO1) between the mirror 2 and the target30 of measurement, an error (PDA) associated with a difference indistance may be obtained from the error data in operation S5.

The calculator 18 may calculate the actual horizontal length (AL) of thetarget 30 of measurement 30 by adjusting the estimated horizontal length(EL1) of the target 30 of measurement obtained from the above with theerror (PDA) associated with the difference in distance, in operation S6.An estimation equation is as follows.

AL=EL/PDA  (Estimation Equation)

The actual horizontal length (AL) of the target 30 of measurement, whichis calculated through adjusting the estimated horizontal length with theerror (PDA) associated with the difference in distance, may be displayedthrough the display unit 14, in operation S7.

Referring to FIG. 3, a method of obtaining an actual lateral length(AL2) of the target 30 of measurement will be described.

First, the calculator 18 estimates a lateral length (EL2) of the target30 of measurement using the ratio of the size of the mobile terminal 10in the picture to the actual size of the mobile terminal 10 in operationS2.

The actual lateral length (AL2) may be calculated by adjusting theestimated lateral length with an error associated with a differencebetween a distance (MTP2) from the mirror 2 and the mobile terminal 10and a distance (MTO2) from the mirror 2 and the target 30 ofmeasurement, in operations S3 through S6.

To adjust the estimated length with the error (PDA) associated with thedistance, in FIG. 3, the distance (MTP2) between the mirror 2 and themobile terminal 10 and the distance (MTO2) between the mirror 2 and thetarget 30 of measurement are obtained in operations S3 and S4.

The distance (MTP2) between the mirror 2 and the mobile terminal 10 maybe obtained from distance data that is obtained in advance throughexperimentation, based on the ratio of the size of the mobile terminal10 in the picture to the actual size of the mobile terminal 10.Therefore, the distance (MTP2) between the mirror 2 and the mobileterminal 10 may be obtained from the distance data stored in thedatabase 15.

In FIG. 3, the distance (MTO2) between the mirror 2 and the target 30 ofmeasurement is a value obtained by subtracting a half (AL1) of theactual horizontal length (AL) of the target 30 of measurement from thedistance (MTP2) between the mirror 2 and the mobile terminal 10. Thedistance (MTP2) between the mirror 2 and the mobile terminal 10 and thehalf (AL1) of the actual horizontal length (AL) of the target 30 ofmeasurement are already obtained and thus, the distance (MTO2) betweenthe mirror 2 and the target 30 of measurement may be also obtained.

After obtaining the distance (MTP2) between the mirror 2 and the mobileterminal 10 and the distance (MTO2) between the mirror 2 and the target30 of measurement, an error (PDA) associated with a difference indistance may be obtained from the error data in operation S5.

The calculator 18 may calculate the actual horizontal length (AL2) ofthe target 30 of measurement 30 by adjusting the estimated horizontallength (EL2) of the target 30 of measurement obtained from the abovewith the error (PDA) associated with the difference in distance, inoperation S6.

The calculated actual lateral length (AL2) may be displayed through thedisplay unit 14, in operation S7.

As described above, the present invention is capable of correcting adistance without a separate distance measurement sensor for measuring adifference in a distance to the mirror between the mobile terminal 10and the target 30 of measurement. Therefore, the present inventionreadily and accurately measures the actual length (AL) of the target 30of measurement.

Although the present embodiment exemplifies that the database 15 and thecalculator 18 are included in the mobile terminal 10, and the calculator18 calculates the actual length of the target 30 of measurement based oninformation stored in the database 15, this may not be limited thereto,and the actual length of the target 30 of measurement may be calculatedusing a length measurement App. downloaded from an online app storeusing the mobile terminal 10. When the actual length of the target 30 ofmeasurement is measured by downloading the length measurement App., thedatabase 15 and the calculator 18 may be included in the central server20. In addition, a calculation program may be included in the lengthmeasurement App., without a separate calculator, and thus, the mobileterminal 10 may calculate the actual length of the target 30 ofmeasurement through the calculation program.

In addition, according to a length measurement method according toanother embodiment of the present invention, a user directly obtainseach pixel value of a size of a mobile terminal and a size of a targetof measurement in a picture, estimates a length of the target ofmeasurement using a ratio of the pixel value of the mobile terminal inthe picture to an actual size of the mobile terminal, and adjusts theestimated length with an error so as to directly calculate the actuallength.

In addition, the user prints out the picture photographed by the mobileterminal 10, obtains the size of the mobile terminal and the size of thetarget of measurement in the picture, estimates the length of the targetof measurement using the ratio of the size of the mobile terminal in thepicture to the actual size of the mobile terminal, and directlycalculates the actual length by adjusting the estimated length with anerror.

Although the present invention has been described with reference to theaccompanying drawings, these are provided for illustrative purposes, andthose skilled in the art would appreciate that various modifications andother equivalent embodiments are possible. Therefore, the scope of thepresent invention shall be determined by the technical ideas of theenclosed claims.

What is claimed is:
 1. A method of measuring a length using a mobileterminal, the method comprising: photographing, by a user, a picture ofthe mobile terminal and a target of measurement together in front of amirror, using a camera of the mobile terminal; obtaining a ratio of asize of the mobile terminal in the picture to an actual size of themobile terminal, and estimating a length of the target of measurementfrom a size of the target of measurement in the picture, using theratio; and calculating an actual length of the target of measurementbased on the estimated length and a difference between a distance fromthe mirror to the mobile terminal and a distance from the mirror to thetarget of measurement.
 2. The method of claim 1, wherein the actual sizeof the mobile terminal is obtained from device type information of themobile terminal.
 3. The method of claim 1, further comprising:executing, by the user, a length measurement Application (App.)downloaded by the mobile terminal.
 4. The method of claim 1, whereincalculating an actual length of the target of measurement comprises:obtaining the distance between the mirror and the mobile terminal;obtaining the distance between the mirror and the target of measurement;obtaining an error associated with the difference between the distancefrom the mirror to the mobile terminal and the distance from the mirrorto the target of measurement; and adjusting the estimated length withthe error.
 5. The method of claim 4, wherein the error is obtained fromerror data that is obtained in advance through experimentation based onthe difference between the distance from the mirror to the mobileterminal and the distance from the mirror to the target of measurement.6. The method of claim 5, wherein the error data is stored in at leastone of the mobile terminal and a central server that communicates withthe mobile terminal.
 7. The method of claim 4, wherein obtaining thedistance between the mirror and the mobile terminal comprises: obtainingthe distance between the mirror and the mobile terminal from distancedata that is obtained in advance through experimentation, based on theratio of the size of the mobile terminal in the picture to the actualsize of the mobile terminal.
 8. The method of claim 7, wherein theactual size of the mobile terminal is obtained from device typeinformation of the mobile terminal stored in at least one of the mobileterminal and a central server that communicates with the mobileterminal.
 9. The method of claim 7, wherein the distance data is storedin at least one of the mobile terminal and a central server thatcommunicates with the mobile terminal.
 10. The method of claim 7,wherein the mobile terminal sets a resolution for photographing to aresolution applied when the distance data is established.
 11. The methodof claim 4, wherein obtaining the distance between the mirror and thetarget of measurement comprises: obtaining the distance between themirror and the mobile terminal, and estimating the distance between themobile terminal and the target of measurement.
 12. The method of claim11, wherein photographing comprises: disposing the target of measurementin the forward direction, in front of the mirror, matching the center ofthe front side of the mobile terminal to the center of the front side ofthe target of measurement, and photographing a picture of the front sideof the target of measurement; and disposing the target of measurement ina lateral direction in front of the mirror, matching the center of thelateral side of the mobile terminal to the center of the front side ofthe target of measurement, and photographing a picture of the lateralside of the target of measurement.
 13. The method of claim 12, obtainingthe distance between the mirror and the target of measurement in thelateral side picture, comprises: estimating an actual horizontal lengthof the target of measurement from the front side picture; estimating adistance between the mirror and the mobile terminal from the lateralside picture; and subtracting a half of the actual horizontal length ofthe target of measurement obtained from the front side picture, from thedistance between the mirror and the mobile terminal, obtained from thelateral side picture.
 14. The method of claim 1, wherein estimating thelength of the target of measurement and the calculating the actuallength of the target of measurement are executed by at least one of themobile terminal and a central server that communicates with the mobileterminal.
 15. The method of claim 1, wherein estimating the length ofthe target of measurement and calculating the actual length of thetarget of measurement are executed by the user who uses the mobileterminal.
 16. The method of claim 15, wherein the user prints out thepicture, directly measures a size of the mobile terminal in the printedpicture, and obtains a ratio of the size of the mobile terminal in thepicture to the actual size of the mobile terminal.
 17. The method ofclaim 15, wherein the user obtains a pixel value associated with thesize of the mobile terminal in the picture using software stored inadvance, and obtains the ratio of the size of the mobile terminal in thepicture to the actual size of the mobile terminal.
 18. A lengthmeasurement system, comprising: a camera that is included in a mobileterminal and photographs a target of measurement in front of a mirror; adatabase that stores an actual size of the mobile terminal and errordata associated with a difference between a distance from the mirror tothe mobile terminal and a distance from the mirror to the target ofmeasurement; and a calculator that obtains a ratio of a size of themobile terminal in the picture to the actual size of the mobileterminal, based on the picture photographed by the camera, estimates alength of the target of measurement from the size of the target ofmeasurement in the picture using the ratio, and adjusts the estimatedlength with the error data, so as to calculate an actual length of thetarget of measurement.